Shiite Muslims

Scott Nelson/World Picture Network, for The New York Times

Shiite Muslims are members of the second largest denomination of Islam, after the Sunnis. They make up only 15 percent of Muslims, but they dominate in Iran, Iraq Azerbaijan and Bahrain, and have a plurality in Lebanon and Yemen.

The groups within Islam first diverged after the Prophet Muhammad died in 632, and his followers could not agree on whether to choose bloodline successors or leaders most likely to follow the tenets of the faith.

The group now known as Sunnis chose Abu Bakr, the prophet’s adviser, to become the first successor, or caliph, to lead the Muslim state. Shiites favored Ali, Muhammad’s cousin and son-in-law. Ali and his successors are called imams, who not only lead the Shiites but are considered to be descendants of Muhammad. After the 11th imam died in 874, and his young son was said to have disappeared from the funeral, Shiites in particular came to see the child as a Messiah who had been hidden from the public by God. The largest sect of Shiites, known as “twelvers,’’ have been preparing for his return ever since.

Violence between the sects began in 656, when the third caliph, revered by the Sunnis, was killed. Soon after, the Sunnis killed Ali’s son Husain.

Sunnis emerged victorious over the Shiites and came to revere the caliphate for its strength and piety. Shiites, by contrast, continued to revere their imams and focus on developing their religious beliefs through them.

In 931 the Twelfth Imam disappeared. This was a turning point in the history of Shi’ism. As R. Scott Appleby, a professor of history at the University of Notre Dame, explained: “Shiite Muslims, who are concentrated in Iran, Iraq, and Lebanon, [believe they] had suffered the loss of divinely guided political leadership” at the time of the Imam’s disappearance. Not “until the ascendancy of Ayatollah Ruhollah Khomeini in 1978” in Iran did Shiites recognize the authority of a legitimate religious figure.

Besides the “twelver” branch, which is the most significant, there are two other branches in Shi’ism: the Ismaili and Zaidi, who dispute the twelver beliefs.

Shiites share fundamental theological beliefs with the Sunnis. They both agree on the five pillars of Islam: 1. the statement of faith that there is no God but God and Mohammed is his messenger; 2. the salah — the requirement to pray five times daily; 3. acceptance of a voluntary religious tax paid directly to the poor; 4. fasting for the entire month of Ramadan, unless physically impossible; 5. performing a pilgrimage to Mecca — the haj — at least once in a lifetime if financially and physically able.

Many Shiites, in addition, make pilgrimages to the holy sites of Najaf, Kerbala, Samarra, and Kazimayn, “the holy thresholds” in Iraq.

--Adapted from "Refresher Course:...Telling Sunni from Shiite," by Damien Cave, Week in Review, The New York Times, Dec. 17, 2006.

The Badr Organization, a Shiite militia, has been effective in fighting the Islamic State, but stands among the most divisive in Iraq, accused of atrocities against Sunnis and known for its close ties to Iran.